Electric discharge tube



March 12, 1935. J BRUUNES 1,994,301

ELECTRIC DISCHARGE TUBE Filed Dec. 11, 1928 Patented Mar. 12, 1935 UNITED ST -ATENT OFFICE ELECTRIC DISCHARGE TUBE Applicationllecember 11, 1928, Serial No. 325,198 In the Netherlands January 18, 1928 4 Claims.

The invention relates to electric discharge tubes, more particularly to those adapted to emit rays, preferably ultra-violet rays, and having a gaseous filling which contains mercury vapour whilst they are preferably provided with an incandescent cathode.

During the operation of such tubes it may occur that mercury condenses on the wall portion through which the rays emerge from the discharge chamber, which causes that a large portion of the rays is absorbed and the efiiciency of the tube is diminished.

The invention has for its object to obviate the said disadvantage or at any rate to reduce it to smaller proportions.

According to the invention, for this purpose so small a quantity of mercury is introduced into the discharge tube that the mercury which might condense during the operation of the tube on the wall portion destined to transmit the rays, is so small that the transmissibility for the rays is substantially not affected.

The invention will be more clearly understood by referring to the accompanying drawing which represents, by way of example, a discharge tube suitable for the irradiation of substances with ultra-violet light. Y

The discharge tube comprises a wall 1, for example of glass, and an incandescent cathode 2- which is secured to the stem3 of the tube. On this stem is also arranged an auxiliary electrode 4 which serves for the ignition. The current-- supply wires of the cathode and the auxiliary electrodes are let out through the stem 3. Anodes 5 and 6 are arranged in side-arms 7 and 8 having stems 9 and. 10 through which the anodes are led out.

Into the tube 1 is sealed a tube 11 consisting of a material adapted totransmit ultra-violet rays, for example of quartz. Into this tube, which is closed at one of its ends and which at its other end has a side-arm 12, is sealed a tube 13 which is open at both ends.

The tube 1 contains a rare gas, for example,

argon and so small a quantity of mercury that.

the mercury which might condense during operation on the tube 11 is so small that the transcan be irradiated with ultra-violet light radiated from the discharge tube.

What I claim is:

l. A mercury vapor lamp for the emission of ultra-violet rays, comprising an elongated tube, a gaseous filling in said tube, at least one anode arranged adjacent one end. of the tube and laterally of the central axis thereof, a thermionic cathode at the other end of the tube, and a double tube formed at least in part of ultra-violet ray transparent material extending into the said first mentioned tube, the two parts of the said last mentioned tube being substantially concen- 1 trio and together forming a tortuous path for the material to be exposed to the ultra-violet radiation.

2. Mercury vapor lamp for the emission of ultraviolet rays, the wall of the lamp consisting at least partly of a material transparent to ultraviolet rays and being in contact with a cooling ultraviolet rays, the wall of the lamp consisting at least partly of a material transparent to ultraviolet rays and being in .contact with a cooling medium, the lamp consisting of an incandescent cathode, an anode, a gas filling and mercury which is wholly in the vaporized state at the operating temperature of the lamp, the mercury present in the lamp being so small that any-mercury which might be condensed in the lamp during operation is so'small that the transmissibility of the ultraviolet rays is not affected.

4. A mercury vapor lamp ,for the emissionof ultraviolet rays, the wall of the lamp comprised at least in part of a material transparent to ultraviolet rays and being in contact with a' cooling medium, the lamp consisting of an incandescent cathode, an anode, a gas filling, and a quantity of mercury which is wholly in the vaporized state, whereby copious quantities of ultraviolet rays are emitted during operation, the transmissibility for the .ultraviolet rays of the wall portion destined for the transmission of said rays being substantially unaffected by mercury which might condense during the operation on said wall portion.

- JOHANNES BRUIJNES. 

